Figure 1. A multistate model describing transition of pigs through the states of shedding following challenge.

At time t an individual is in state i. Its 5 states are labeled 1, 2, 3, 4, and 5, denoting: 1-latency: the individual has been challenged but has not yet started (or will never start) shedding; 2-continuous shedding state; 3-intermittent non-shedding state; 4-intermittent shedding state; and 5-recovery: clearance of Salmonella from feces. Gray shaded compartments denote the pigs that excrete detectable levels of Salmonella in feces.